/*
** $Id: ltablib.c,v 1.93.1.1 2017/04/19 17:20:42 roberto Exp $
** Library for Table Manipulation
** See Copyright Notice in lua.h
*/

#define ltablib_c
#define LUA_LIB

#include "lprefix.h"

#include <limits.h>
#include <stddef.h>
#include <string.h>

#include "lua.h"

#include "lauxlib.h"
#include "lualib.h"

/*
** Operations that an object must define to mimic a table
** (some functions only need some of them)
*/
#define TAB_R 1                /* read */
#define TAB_W 2                /* write */
#define TAB_L 4                /* length */
#define TAB_RW (TAB_R | TAB_W) /* read/write */

#define aux_getn(L, n, w) (checktab(L, n, (w) | TAB_L), luaL_len(L, n))

static int checkfield(lua_State *L, const char *key, int n)
{
  lua_pushstring(L, key);
  return (lua_rawget(L, -n) != LUA_TNIL);
}

/*
** Check that 'arg' either is a table or can behave like one (that is,
** has a metatable with the required metamethods)
*/
static void checktab(lua_State *L, int arg, int what)
{
  if (lua_type(L, arg) != LUA_TTABLE)
  {                                 /* is it not a table? */
    int n = 1;                      /* number of elements to pop */
    if (lua_getmetatable(L, arg) && /* must have metatable */
        (!(what & TAB_R) || checkfield(L, "__index", ++n)) &&
        (!(what & TAB_W) || checkfield(L, "__newindex", ++n)) &&
        (!(what & TAB_L) || checkfield(L, "__len", ++n)))
    {
      lua_pop(L, n); /* pop metatable and tested metamethods */
    }
    else
      luaL_checktype(L, arg, LUA_TTABLE); /* force an error */
  }
}

#if defined(LUA_COMPAT_MAXN)
static int maxn(lua_State *L)
{
  lua_Number max = 0;
  luaL_checktype(L, 1, LUA_TTABLE);
  lua_pushnil(L); /* first key */
  while (lua_next(L, 1))
  {
    lua_pop(L, 1); /* remove value */
    if (lua_type(L, -1) == LUA_TNUMBER)
    {
      lua_Number v = lua_tonumber(L, -1);
      if (v > max)
        max = v;
    }
  }
  lua_pushnumber(L, max);
  return 1;
}
#endif

static int tinsert(lua_State *L)
{
  lua_Integer e = aux_getn(L, 1, TAB_RW) + 1; /* first empty element */
  lua_Integer pos;                            /* where to insert new element */
  switch (lua_gettop(L))
  {
  case 2:
  {          /* called with only 2 arguments */
    pos = e; /* insert new element at the end */
    break;
  }
  case 3:
  {
    lua_Integer i;
    pos = luaL_checkinteger(L, 2); /* 2nd argument is the position */
    luaL_argcheck(L, 1 <= pos && pos <= e, 2, "position out of bounds");
    for (i = e; i > pos; i--)
    { /* move up elements */
      lua_geti(L, 1, i - 1);
      lua_seti(L, 1, i); /* t[i] = t[i - 1] */
    }
    break;
  }
  default:
  {
    return luaL_error(L, "wrong number of arguments to 'insert'");
  }
  }
  lua_seti(L, 1, pos); /* t[pos] = v */
  return 0;
}

static int tremove(lua_State *L)
{
  lua_Integer size = aux_getn(L, 1, TAB_RW);
  lua_Integer pos = luaL_optinteger(L, 2, size);
  if (pos != size) /* validate 'pos' if given */
    luaL_argcheck(L, 1 <= pos && pos <= size + 1, 1, "position out of bounds");
  lua_geti(L, 1, pos); /* result = t[pos] */
  for (; pos < size; pos++)
  {
    lua_geti(L, 1, pos + 1);
    lua_seti(L, 1, pos); /* t[pos] = t[pos + 1] */
  }
  lua_pushnil(L);
  lua_seti(L, 1, pos); /* t[pos] = nil */
  return 1;
}

/*
** Copy elements (1[f], ..., 1[e]) into (tt[t], tt[t+1], ...). Whenever
** possible, copy in increasing order, which is better for rehashing.
** "possible" means destination after original range, or smaller
** than origin, or copying to another table.
*/
static int tmove(lua_State *L)
{
  lua_Integer f = luaL_checkinteger(L, 2);
  lua_Integer e = luaL_checkinteger(L, 3);
  lua_Integer t = luaL_checkinteger(L, 4);
  int tt = !lua_isnoneornil(L, 5) ? 5 : 1; /* destination table */
  checktab(L, 1, TAB_R);
  checktab(L, tt, TAB_W);
  if (e >= f)
  { /* otherwise, nothing to move */
    lua_Integer n, i;
    luaL_argcheck(L, f > 0 || e < LUA_MAXINTEGER + f, 3,
                  "too many elements to move");
    n = e - f + 1; /* number of elements to move */
    luaL_argcheck(L, t <= LUA_MAXINTEGER - n + 1, 4,
                  "destination wrap around");
    if (t > e || t <= f || (tt != 1 && !lua_compare(L, 1, tt, LUA_OPEQ)))
    {
      for (i = 0; i < n; i++)
      {
        lua_geti(L, 1, f + i);
        lua_seti(L, tt, t + i);
      }
    }
    else
    {
      for (i = n - 1; i >= 0; i--)
      {
        lua_geti(L, 1, f + i);
        lua_seti(L, tt, t + i);
      }
    }
  }
  lua_pushvalue(L, tt); /* return destination table */
  return 1;
}

static void addfield(lua_State *L, luaL_Buffer *b, lua_Integer i)
{
  lua_geti(L, 1, i);
  if (!lua_isstring(L, -1))
    luaL_error(L, "invalid value (%s) at index %d in table for 'concat'",
               luaL_typename(L, -1), i);
  luaL_addvalue(b);
}

static int tconcat(lua_State *L)
{
  luaL_Buffer b;
  lua_Integer last = aux_getn(L, 1, TAB_R);
  size_t lsep;
  const char *sep = luaL_optlstring(L, 2, "", &lsep);
  lua_Integer i = luaL_optinteger(L, 3, 1);
  last = luaL_optinteger(L, 4, last);
  luaL_buffinit(L, &b);
  for (; i < last; i++)
  {
    addfield(L, &b, i);
    luaL_addlstring(&b, sep, lsep);
  }
  if (i == last) /* add last value (if interval was not empty) */
    addfield(L, &b, i);
  luaL_pushresult(&b);
  return 1;
}

/*
** {======================================================
** Pack/unpack
** =======================================================
*/

static int pack(lua_State *L)
{
  int i;
  int n = lua_gettop(L);    /* number of elements to pack */
  lua_createtable(L, n, 1); /* create result table */
  lua_insert(L, 1);         /* put it at index 1 */
  for (i = n; i >= 1; i--)  /* assign elements */
    lua_seti(L, 1, i);
  lua_pushinteger(L, n);
  lua_setfield(L, 1, "n"); /* t.n = number of elements */
  return 1;                /* return table */
}

static int unpack(lua_State *L)
{
  lua_Unsigned n;
  lua_Integer i = luaL_optinteger(L, 2, 1);
  lua_Integer e = luaL_opt(L, luaL_checkinteger, 3, luaL_len(L, 1));
  if (i > e)
    return 0;              /* empty range */
  n = (lua_Unsigned)e - i; /* number of elements minus 1 (avoid overflows) */
  if (n >= (unsigned int)INT_MAX || !lua_checkstack(L, (int)(++n)))
    return luaL_error(L, "too many results to unpack");
  for (; i < e; i++)
  { /* push arg[i..e - 1] (to avoid overflows) */
    lua_geti(L, 1, i);
  }
  lua_geti(L, 1, e); /* push last element */
  return (int)n;
}

/* }====================================================== */

/*
** {======================================================
** Quicksort
** (based on 'Algorithms in MODULA-3', Robert Sedgewick;
**  Addison-Wesley, 1993.)
** =======================================================
*/

/* type for array indices */
typedef unsigned int IdxT;

/*
** Produce a "random" 'unsigned int' to randomize pivot choice. This
** macro is used only when 'sort' detects a big imbalance in the result
** of a partition. (If you don't want/need this "randomness", ~0 is a
** good choice.)
*/
#if !defined(l_randomizePivot) /* { */

#include <time.h>

/* size of 'e' measured in number of 'unsigned int's */
#define sof(e) (sizeof(e) / sizeof(unsigned int))

/*
** Use 'time' and 'clock' as sources of "randomness". Because we don't
** know the types 'clock_t' and 'time_t', we cannot cast them to
** anything without risking overflows. A safe way to use their values
** is to copy them to an array of a known type and use the array values.
*/
static unsigned int l_randomizePivot(void)
{
  clock_t c = clock();
  time_t t = time(NULL);
  unsigned int buff[sof(c) + sof(t)];
  unsigned int i, rnd = 0;
  memcpy(buff, &c, sof(c) * sizeof(unsigned int));
  memcpy(buff + sof(c), &t, sof(t) * sizeof(unsigned int));
  for (i = 0; i < sof(buff); i++)
    rnd += buff[i];
  return rnd;
}

#endif /* } */

/* arrays larger than 'RANLIMIT' may use randomized pivots */
#define RANLIMIT 100u

static void set2(lua_State *L, IdxT i, IdxT j)
{
  lua_seti(L, 1, i);
  lua_seti(L, 1, j);
}

/*
** Return true iff value at stack index 'a' is less than the value at
** index 'b' (according to the order of the sort).
*/
static int sort_comp(lua_State *L, int a, int b)
{
  if (lua_isnil(L, 2))                     /* no function? */
    return lua_compare(L, a, b, LUA_OPLT); /* a < b */
  else
  { /* function */
    int res;
    lua_pushvalue(L, 2);        /* push function */
    lua_pushvalue(L, a - 1);    /* -1 to compensate function */
    lua_pushvalue(L, b - 2);    /* -2 to compensate function and 'a' */
    lua_call(L, 2, 1);          /* call function */
    res = lua_toboolean(L, -1); /* get result */
    lua_pop(L, 1);              /* pop result */
    return res;
  }
}

/*
** Does the partition: Pivot P is at the top of the stack.
** precondition: a[lo] <= P == a[up-1] <= a[up],
** so it only needs to do the partition from lo + 1 to up - 2.
** Pos-condition: a[lo .. i - 1] <= a[i] == P <= a[i + 1 .. up]
** returns 'i'.
*/
static IdxT partition(lua_State *L, IdxT lo, IdxT up)
{
  IdxT i = lo;     /* will be incremented before first use */
  IdxT j = up - 1; /* will be decremented before first use */
  /* loop invariant: a[lo .. i] <= P <= a[j .. up] */
  for (;;)
  {
    /* next loop: repeat ++i while a[i] < P */
    while (lua_geti(L, 1, ++i), sort_comp(L, -1, -2))
    {
      if (i == up - 1) /* a[i] < P  but a[up - 1] == P  ?? */
        luaL_error(L, "invalid order function for sorting");
      lua_pop(L, 1); /* remove a[i] */
    }
    /* after the loop, a[i] >= P and a[lo .. i - 1] < P */
    /* next loop: repeat --j while P < a[j] */
    while (lua_geti(L, 1, --j), sort_comp(L, -3, -1))
    {
      if (j < i) /* j < i  but  a[j] > P ?? */
        luaL_error(L, "invalid order function for sorting");
      lua_pop(L, 1); /* remove a[j] */
    }
    /* after the loop, a[j] <= P and a[j + 1 .. up] >= P */
    if (j < i)
    { /* no elements out of place? */
      /* a[lo .. i - 1] <= P <= a[j + 1 .. i .. up] */
      lua_pop(L, 1); /* pop a[j] */
      /* swap pivot (a[up - 1]) with a[i] to satisfy pos-condition */
      set2(L, up - 1, i);
      return i;
    }
    /* otherwise, swap a[i] - a[j] to restore invariant and repeat */
    set2(L, i, j);
  }
}

/*
** Choose an element in the middle (2nd-3th quarters) of [lo,up]
** "randomized" by 'rnd'
*/
static IdxT choosePivot(IdxT lo, IdxT up, unsigned int rnd)
{
  IdxT r4 = (up - lo) / 4; /* range/4 */
  IdxT p = rnd % (r4 * 2) + (lo + r4);
  lua_assert(lo + r4 <= p && p <= up - r4);
  return p;
}

/*
** QuickSort algorithm (recursive function)
*/
static void auxsort(lua_State *L, IdxT lo, IdxT up,
                    unsigned int rnd)
{
  while (lo < up)
  {         /* loop for tail recursion */
    IdxT p; /* Pivot index */
    IdxT n; /* to be used later */
    /* sort elements 'lo', 'p', and 'up' */
    lua_geti(L, 1, lo);
    lua_geti(L, 1, up);
    if (sort_comp(L, -1, -2)) /* a[up] < a[lo]? */
      set2(L, lo, up);        /* swap a[lo] - a[up] */
    else
      lua_pop(L, 2);                    /* remove both values */
    if (up - lo == 1)                   /* only 2 elements? */
      return;                           /* already sorted */
    if (up - lo < RANLIMIT || rnd == 0) /* small interval or no randomize? */
      p = (lo + up) / 2;                /* middle element is a good pivot */
    else                                /* for larger intervals, it is worth a random pivot */
      p = choosePivot(lo, up, rnd);
    lua_geti(L, 1, p);
    lua_geti(L, 1, lo);
    if (sort_comp(L, -2, -1)) /* a[p] < a[lo]? */
      set2(L, p, lo);         /* swap a[p] - a[lo] */
    else
    {
      lua_pop(L, 1); /* remove a[lo] */
      lua_geti(L, 1, up);
      if (sort_comp(L, -1, -2)) /* a[up] < a[p]? */
        set2(L, p, up);         /* swap a[up] - a[p] */
      else
        lua_pop(L, 2);
    }
    if (up - lo == 2)       /* only 3 elements? */
      return;               /* already sorted */
    lua_geti(L, 1, p);      /* get middle element (Pivot) */
    lua_pushvalue(L, -1);   /* push Pivot */
    lua_geti(L, 1, up - 1); /* push a[up - 1] */
    set2(L, p, up - 1);     /* swap Pivot (a[p]) with a[up - 1] */
    p = partition(L, lo, up);
    /* a[lo .. p - 1] <= a[p] == P <= a[p + 1 .. up] */
    if (p - lo < up - p)
    {                             /* lower interval is smaller? */
      auxsort(L, lo, p - 1, rnd); /* call recursively for lower interval */
      n = p - lo;                 /* size of smaller interval */
      lo = p + 1;                 /* tail call for [p + 1 .. up] (upper interval) */
    }
    else
    {
      auxsort(L, p + 1, up, rnd); /* call recursively for upper interval */
      n = up - p;                 /* size of smaller interval */
      up = p - 1;                 /* tail call for [lo .. p - 1]  (lower interval) */
    }
    if ((up - lo) / 128 > n)    /* partition too imbalanced? */
      rnd = l_randomizePivot(); /* try a new randomization */
  }                             /* tail call auxsort(L, lo, up, rnd) */
}

static int sort(lua_State *L)
{
  lua_Integer n = aux_getn(L, 1, TAB_RW);
  if (n > 1)
  { /* non-trivial interval? */
    luaL_argcheck(L, n < INT_MAX, 1, "array too big");
    if (!lua_isnoneornil(L, 2))            /* is there a 2nd argument? */
      luaL_checktype(L, 2, LUA_TFUNCTION); /* must be a function */
    lua_settop(L, 2);                      /* make sure there are two arguments */
    auxsort(L, 1, (IdxT)n, 0);
  }
  return 0;
}

/* }====================================================== */

static const luaL_Reg tab_funcs[] = {
    {"concat", tconcat},
#if defined(LUA_COMPAT_MAXN)
    {"maxn", maxn},
#endif
    {"insert", tinsert},
    {"pack", pack},
    {"unpack", unpack},
    {"remove", tremove},
    {"move", tmove},
    {"sort", sort},
    {NULL, NULL}};

LUAMOD_API int luaopen_table(lua_State *L)
{
  luaL_newlib(L, tab_funcs);
#if defined(LUA_COMPAT_UNPACK)
  /* _G.unpack = table.unpack */
  lua_getfield(L, -1, "unpack");
  lua_setglobal(L, "unpack");
#endif
  return 1;
}
